The overall goal of this project is to develop a computer-aided system that can assist the radiologist in targeting small pulmonary nodules during CT-guided lung biopsy. The estimated 3D needle trajectory along with the range of potential needle trajectories given varying degrees of needle steering will be calculated and displayed to the radiologist. We believe that such an interactive guidance system can enhance the ability of the radiologist to successfully biopsy small nodules. Lung biopsy is an important clinical problem and the ability to successfully biopsy small nodules in the lung depends greatly on the skill of the physician. Small lung nodules are now being detected with increasing frequency and CTguided transthoracic needle biopsy is the method of choice to obtain tissue for a pathologically confirmed diagnosis. This is an STTR Phase I proposal which is focused on demonstrating the feasibility of our approach. During Phase I, we will develop and evaluate the key components of our computer-aided guidance system along with a prototype user interface. Algorithm development and evaluation will be done using an existing database of clinical images. In Phase II, we will further integrate these components into a visualization system to provide on-line computer assistance during the lung biopsy procedure and conduct a clinical trial. The ultimate goal of this work is to develop and sell this technology as a lung biopsy guidance product. This proposal is a three-way partnership between a Medical Center with extensive clinical expertise in lung biopsy (Weill-Cornell Medical Center, New York, NY), a small business with experience in software development and medical visualization (Kitware Inc., Clifton Park, NY), and a University-based research group specializing in technology development for image-guided procedures (Georgetown University, Washington, DC). This is a highly innovative and important project in that such a system does not exist and this is a novel method of providing on-line guidance to the radiologist during CTguided lung biopsy. The specific aims of the research are to: 1. Develop and evaluate the key components of a computer-aided system for targeting of small nodules during lung biopsy including a) locating the biopsy needle and tip; b) tracking the target nodule; and c) estimating the 3D path of the needle. 2. Develop and evaluate a prototype user interface incorporating these components which displays the target nodule relative to the location of the needle tip and provides the radiologist with a visual display of how to advance the needle towards the target. [unreadable] [unreadable] [unreadable]